Method for depicting structure-lithology composite trap

Abstract

The invention relates to a method for depicting a structure-lithology composite trap, and belongs to the field of rolling exploration and development of petroleum and natural gas. The method comprises the following steps: acquiring seismic data of a target area and well logging data and well drilling data of a known well; carrying out contiguous structure seismic interpretation on the target layer section of the target area, and making a target layer structure map; determining the sedimentary facies type of the target area according to the corresponding relation between the typical landmark shape of the seismic phase and the sedimentary facies type; determining a seismic phase and a feature on a seismic section corresponding to the target layer section reservoir; establishing a corresponding relation between the lithologic density and the lithology of the stratum of the target layer section; determining the boundary line position of the reservoir boundary line of the target layer section on the plane graph; and determining a structure-lithology composite trap by combining the target layer structure map and the boundary line position of the sandstone reservoir boundary line of the target layer section on the plane map. According to the method, the problem of low reservoir prediction precision caused by misjudgment due to a multi-solution problem when reservoir prediction is carried out by using a seismic phase in an existing method is solved.

Description

Technical Field

[0001] The present invention belongs to the field of rolling exploration and development of oil and gas, and particularly relates to a method for characterizing a structural-lithologic composite trap. Background Art

[0002] In oil and gas field exploration and development, it is necessary to search for oil and gas traps. The commonly used method for searching for traps at present is: through seismic interpretation, searching for structural traps; long-term single-structural trap search has led to the near exhaustion of this type of resources and it is difficult to meet the needs of the later production of the oilfield. Characterizing structural-lithologic composite traps to increase reserves is a new technology to meet the needs of the later production of the oilfield.

[0003] A structural-lithologic composite trap refers to an area rich in oil and gas where a fault or a lithologic annihilation boundary cannot form an oil and gas trap of a single factor alone. It requires the combination of a fault and a lithologic annihilation boundary to form a complete and enclosed structural-lithologic composite trap for storing oil and gas. This technology is applicable to oil and gas enrichment areas with the formation conditions of structural-lithologic composite traps. Based on the structural and sedimentary facies results of the target interval in the target area, the favorable areas considered to meet the conditions through research and analysis are used as the target research areas for characterizing structural-lithologic composite traps.

[0004] Using the existing technology to characterize structural-lithologic composite traps requires the cooperation of two processes: structural interpretation and reservoir prediction, and reservoir prediction is carried out after the structural interpretation is completed. In terms of predicting the reservoir boundary, the main methods of the existing technology are seismic attribute extraction and seismic inversion. The application effects of these two methods in continental strata are relatively poor. The reason is that the continental strata have poor stability. When tracking the target horizon, various changes such as fuzziness, displacement, bifurcation, distortion, disappearance, and phase disorder of the tracked target horizon often occur, resulting in the phenomenon of cross-strata and misaligned strata of the tracked horizon and repeated modification of the tracking results of the target horizon. Therefore, according to the window value given by reservoir prediction personnel based on experience - that is, between two parallel planes with a certain distance above and below the tracked target horizon, the seismic signals at each point are captured and picked up by a computer, and after being processed by professional technicians, the seismic attribute result maps such as wave impedance, amplitude, instantaneous phase, and half-amplitude energy of these points are output. Through the analysis of reservoir prediction technicians, the development and distribution boundaries of the target sandstone reservoir are determined. Due to the complexity of the sedimentary environment of continental strata, the lithology types of continental deposits are complex and diverse. Reservoir prediction is carried out based on the reflected waves and seismic phases between the reservoir and its upper and lower surrounding rocks in such a sedimentary environment. The corresponding reservoir information carried by the seismic phase is determined by the density difference between the reservoir and the surrounding rocks. However, the same density difference can correspond to multiple lithologic combinations. Therefore, when using seismic phases for reservoir prediction, misjudgments often occur due to the problem of multiple solutions. In addition, the tracking of continental strata is difficult and the error rate of tracking is high. When picking up seismic signals along the tracked target horizon according to a fixed window value, phenomena such as overflow of effective seismic signals and intrusion of invalid signals are likely to occur, resulting in deviation of the reservoir prediction results and poor application effects. Summary of the Invention

[0005] The object of the present invention is to provide a method for characterizing a structural-lithologic composite trap, so as to solve the problem that when the existing method for identifying traps uses seismic phases for reservoir prediction, misjudgment often occurs due to the multi-solution problem, resulting in low accuracy of reservoir prediction.

[0006] The method for characterizing a structural-lithologic composite trap provided by the present invention to solve the above technical problems includes the following steps:

[0007] 1) Obtain seismic data of the target area, logging data and drilling data of known wells;

[0008] 2) Use the seismic data to conduct continuous structural interpretation of the target interval in the target area and make a structural map of the target interval;

[0009] 3) During the continuous structural interpretation process, determine the sedimentary facies type of the target area according to the corresponding relationship between the typical landmark shape of the seismic phase and the sedimentary facies type;

[0010] 4) Use the logging data and drilling data of the known wells to determine the seismic phase and characteristics corresponding to the sandstone reservoir in the target interval of the target area;

[0011] 5) Based on the provenance of the target area and the drilling data on both sides, determine the lithology types of the strata in the same interval of the target area, and establish a corresponding linear relationship between the formation lithology density and lithology in the target interval of the target area;

[0012] 6) According to the corresponding linear relationship established in step 5), under the constraint of the sedimentary facies in the target area, determine the density distribution corresponding to the sandstone reservoir in the target interval, and combine the seismic phase characteristics corresponding to the sandstone reservoir in the target interval determined in step 4) to determine the distribution and boundary line position of the sandstone reservoir in the target interval on the plane map;

[0013] 7) Combine the structural map of the target interval with the distribution and boundary line position of the sandstone reservoir in the target interval on the plane map to determine the structural-lithologic composite trap.

[0014] The beneficial effects of the present invention are as follows: The present invention characterizes the structural-lithologic composite oil and gas trap, uses the seismic phase of searching for typical landmark forms to determine the sedimentary facies type of the target area, and under the constraint of the sedimentary facies, determines the lithology types of the same interval in the target area based on the provenance of the target area and drilling data, solves the multi-solution problem of reservoir prediction, and further solves the problems of large error and poor effect of the prediction result caused by the multi-solution problem, and improves the prediction accuracy. In addition, the characterization method of the present invention can be realized only through one process of seismic interpretation, which improves the efficiency and reduces the cost.

[0015] Further, in step 1), the target area is selected in the following way: by using the oil and gas distribution map of the oilfield, studying the planar law of oil and gas distribution and the oil-bearing formation intervals in the oilfield, determining the oil and gas enrichment zones and oil-bearing formation intervals in the oilfield; based on the sedimentary facies results of the oil-bearing formation intervals in the oil and gas enrichment zones, selecting the target area in the potential oil and gas accumulation areas with the formation conditions of structural-lithologic composite traps. By using the oil and gas distribution map of the oilfield to study the planar law of oil and gas distribution and the oil-bearing formation intervals in the oilfield, the accuracy of determining the oil and gas enrichment zones and oil-bearing formation intervals can be improved, and thus the target area can be accurately found.

[0016] Further, in order to determine the sedimentary facies type of the target area faster and more accurately, in step 3), during the continuous structural seismic interpretation process, under the waveform display mode of the seismic section phase, by using the mutual conversion of the positive and negative polarities of the seismic phase waveform, observing and searching for the typical landmark shapes under the positive or negative polarity display mode of the seismic phase near the target interval, and using the corresponding relationship between the typical landmark shapes of the seismic phase and the sedimentary facies type, the sedimentary facies type of the target area is determined.

[0017] Further, if the formation corresponding to the seismic phase of the typical landmark shape does not completely coincide with the target interval, dissect the cross-section at the center position of the seismic phase of the typical landmark shape. If the seismic phase corresponding to the target interval is consistent with the morphology of the seismic phase of the typical landmark shape and has a similar distribution law, or if the target formation is sandwiched between the formations corresponding to the seismic phases of two typical landmark shapes and the seismic phase corresponding to the target interval is approximately the same as the morphologies of the seismic phases of the two typical landmark shapes, then the sedimentary facies type of the formation corresponding to the seismic phase of the typical landmark shape is the sedimentary facies type of the target interval in the target area. By dissecting the cross-section at the center position of the seismic phase of the typical landmark shape and judging the seismic phase morphology and distribution law, the sedimentary facies type of the target interval in the target area can be further confirmed, and the reliability of sedimentary facies type judgment can be improved.

[0018] Further, in order to more reliably determine the seismic phase on the seismic section corresponding to the target interval in the target area, in step 4), the process of determining the seismic phase and characteristics corresponding to the sandstone reservoir of the target interval in the target area by using the logging data and drilling data of the known well is as follows: making a synthetic seismogram by using the logging data of the known well, establishing a one-to-one correspondence between the formations drilled by the known well and the seismic phase of the well-side trace of the well, using the corresponding relationship between the known well and the seismic phase of the well-side trace of the well to determine the target sandstone reservoir drilled by the known well and the seismic phase on the corresponding seismic section, using the relationship between the top and bottom positions of the sandstone reservoir marked on the well trajectory and the seismic phase to determine the positions of the top and bottom of the corresponding sandstone reservoir on the seismic phase, and tracking and interpreting the seismic phase to determine the distribution and characteristics of the seismic phase corresponding to the sandstone reservoir of the target interval in the target area.

[0019] Further, in order to more reliably establish the corresponding relationship between the density and lithology of the target interval in the target area, in step 5), the process of establishing the corresponding linear relationship between the lithology density and lithology of the target interval in the target area is as follows: Determine the provenance direction of the target area through sedimentary facies results. Based on the lithology types of the target interval strata revealed by the wells on both sides of the provenance of the target area, determine the lithology types of the strata in the same interval in the target area. Use the electric logging density curve data of the surrounding wells to establish a one-to-one correspondence between the density and lithology of the target interval in the target area.

[0020] Further, in the process of determining the position of the boundary line of the sandstone reservoir in the target interval on the plane map, set the seismic phase display color scale corresponding to the target sandstone reservoir in the target area determined in step 4) as a multi-color color scale method, so as to synthesize the seismic variable density phase color system boundary line corresponding to the marked boundary of the sandstone reservoir in the target interval on the well trajectory of the synthetic record well as the boundary line of the target sandstone reservoir. Through tracing and interpretation, determine the boundary line of the target sandstone reservoir in the target area in the profile; Through the continuous tracing and interpretation of the seismic phase, determine the position of the boundary line of the target sandstone reservoir in the target area on the plane map.

[0021] Use the setting of the high-sensitivity multi-color color scale display method of seismic phase variable density, and use the variable density seismic phase color system to correspond to the demarcation of the sandstone reservoir marked on the well trajectory of the synthetic record well to determine the boundary of the target sandstone reservoir, and then determine the boundary line of the target sandstone reservoir in the target area, so as to quantify the confirmation of the reservoir lithology boundary.

[0022] Further, in order to more accurately depict the structural-lithological composite trap, in step 7), superpose the structural map of the target interval and the position of the boundary line of the sandstone reservoir in the target interval in the target area on the plane map in equal proportion. The trap formed by the combination of faults and the annihilation boundary line of the sandstone reservoir is the depicted structural-lithological composite trap.

[0023] Further, in step 5), when the lithology types of the target interval in the target area are only sandstone and mudstone, the corresponding relationship between the density and lithology of the target interval in the target area is: high density corresponds to mudstone, and low density corresponds to sandstone.

[0024] Further, in step 4), the known well is a standard well selected nearby in the same structural zone in the vicinity of the target area. By making synthetic records for the wells selected nearby in the target area, establish a one-to-one correspondence between the strata drilled by the well and the seismic phase. Through the close-range seismic phase tracing, determine the seismic phase corresponding to the target reservoir in the target area, reduce the risk of error increase in the tracing process, and further improve the prediction accuracy. Description of the Drawings

[0025] Figure 1 It is a flowchart of the method according to the embodiment of the present invention;

[0026] Figure 2Sedimentary microfacies map of the target layer series in the research area of the embodiment of the present invention;

[0027] Figure 3 Top structure map of the target layer in the research area of the embodiment of the present invention;

[0028] Figure 4 Plan view of the seismic phase tracking and interpretation results of the typical landmark shapes in the embodiment of the present invention;

[0029] Figure 5 Seismic profile across the A-A1 profile line in the embodiment of the present invention;

[0030] Figure 6 Seismic profile across the B-B1 profile line in the embodiment of the present invention;

[0031] Figure 7 Schematic diagram for dividing the stratigraphic range of the same sedimentary facies in the confirmed research area in the embodiment of the present invention;

[0032] Figure 8 Synthetic seismogram of Well V339 selected nearby the target area in the embodiment of the present invention;

[0033] Figure 9 Schematic diagram of the correspondence between the synthetic seismogram of Well V339 selected nearby the target area and the seismic phase;

[0034] Figure 10 Enlarged view of the drilling result of the target layer at the bottom of the third member of the Shahejie Formation encountered by the well in the embodiment of the present invention;

[0035] Figure 11 Schematic diagram of the seismic phase tracking results corresponding to the target sandstone reservoir of the synthetic record well in the embodiment of the present invention;

[0036] Figure 12 Cross-sectional diagram of the variable density seismic phase corresponding to the target sandstone reservoir in the target area in the embodiment of the present invention;

[0037] Figure 13 Contact cross-sectional diagram of the variable density seismic phase corresponding to the target sandstone reservoir;

[0038] Figure 14 Schematic diagram for selecting the multi-color system of the color scale of the variable density seismic profile in the embodiment of the present invention;

[0039] Figure 15 Enlarged schematic diagram of the drilling result of the top structure-lithology composite trap of the target layer in the embodiment of the present invention;

[0040] Figure 16 Schematic diagram of the top structure-lithology composite trap of the target layer in the embodiment of the present invention. Detailed implementation manners

[0041] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0042] As Figure 1 shown, the method for characterizing the structural-lithologic composite trap of the present invention includes the following steps:

[0043] 1) Obtain seismic data, logging data, and drilling data of the target area;

[0044] 2) Use the seismic data to conduct continuous structural interpretation of the target interval in the target area and produce a structural map of the target interval;

[0045] 3) During the continuous structural interpretation process, determine the sedimentary facies types in the target area according to the corresponding relationship between the typical landmark shapes of seismic phases and sedimentary facies types;

[0046] 4) Use the logging data and drilling data of the known wells to determine the seismic phases and characteristics corresponding to the sandstone reservoirs in the target interval of the target area;

[0047] 5) Based on the provenance in the target area and the drilling data on both sides, determine the lithology types of the strata in the same interval in the target area, and establish a corresponding linear relationship between the formation lithology density and lithology in the target interval of the target area;

[0048] 6) According to the corresponding linear relationship established in step 5), under the constraint of the sedimentary facies in the target area, determine the density distribution corresponding to the sandstone reservoirs in the target interval, and combine the seismic phase characteristics corresponding to the sandstone reservoirs in the target interval determined in step 4) to determine the distribution and boundary line position of the sandstone reservoirs in the target interval on the plane map;

[0049] 7) Combine the structural map of the target interval with the distribution and boundary line position of the sandstone reservoirs in the target interval on the plane map to determine the structural-lithologic composite trap.

[0050] Other embodiments of each step in the above embodiments will be described below.

[0051] I. Obtain seismic data, logging data, and drilling data of the target area: The selection process of the target area is as follows: According to the study of the sedimentary facies of the hydrocarbon-rich intervals in the hydrocarbon-rich belts of the oilfield, select the areas with the formation conditions of structural-lithologic composite traps in the study work area as the target area.

[0052] In this embodiment, a method for selecting the hydrocarbon-rich belts of the oilfield is given. Specifically, use the hydrocarbon distribution map of the selected oilfield to conduct research on the plane law of hydrocarbon distribution and the main hydrocarbon-bearing intervals of the selected oilfield, and determine the hydrocarbon-rich areas and hydrocarbon-rich intervals of the selected oilfield.

[0053] After selecting the hydrocarbon-rich zones and intervals in the selected oilfield, the target study area is selected in the potential hydrocarbon accumulation areas with the formation conditions of structural-lithologic composite traps according to the sedimentary facies results of the hydrocarbon-rich intervals in the hydrocarbon-rich zones.

[0054] Combined with Figure 2 A further explanation of this step is as follows: First, use the hydrocarbon-bearing situation results revealed by the previous drilling in the study area and the data such as development well testing and production testing to study the hydrocarbon distribution law in the study area; select the main oil-bearing series in the downthrown block of the target fault in the study area. The hydrocarbon enrichment degree of this series is high, and the main oil-bearing interval in the downthrown block of the target fault in the study area is determined as the target oil-bearing interval, which is used as the target interval of the next-step rolling exploration target area.

[0055] After determining the target oil-bearing interval in the downthrown block of the target fault in the study area, according to the sedimentary facies results of the strata in the target interval of the study area, such as Figure 2 shown, turbidite fans develop in the target interval of the downthrown block of the target fault, and there are conditions for forming fault-lithologic hydrocarbon composite traps in combination with the target fault. Therefore, the target interval of the downthrown block of the target fault is preferably delineated as the target interval of the target area.

[0056] II. Interpretation of structure: Use seismic data to conduct contiguous structure interpretation of the target horizon in the target area and make a structure map of the target horizon.

[0057] As another implementation, when making the structure map of the target horizon, the distribution of the proven petroleum reserves in the target horizon is also marked, such as Figure 3 shown.

[0058] III. Determination of sedimentary facies types: During the contiguous structure seismic interpretation process, determine the sedimentary facies types in the target area according to the corresponding relationship between the typical landmark shapes of seismic phases and sedimentary facies types.

[0059] As an implementation, during the contiguous structure seismic interpretation process, use the positive and negative polarity conversion of seismic phases, and at the same time observe and search for the typical landmark shapes of seismic phases. Use the typical landmark shapes of these seismic phases to characterize the characteristics of a sedimentary facies type, and determine the sedimentary facies type of the strata corresponding to the seismic phases with typical landmark shapes. Thus, determine the sedimentary facies types of the target intervals.

[0060] Specifically, first, during the structure interpretation process, set the seismic profile phase display mode to the waveform display form, use the positive and negative polarity conversion of the seismic phase waveform, and observe and search for the typical landmark shapes in the positive or negative polarity display mode of the seismic phase near the target horizon. Use the typical landmark shapes of these seismic phases to characterize the characteristics of a sedimentary facies type, and determine the sedimentary facies type of the strata corresponding to the seismic phases with typical landmark shapes.

[0061] Then, it is judged whether the formation corresponding to the typical signature shape seismic phase coincides with the target interval. In the case where the two do not completely coincide, by dissecting the cross-section at the center position of the typical signature shape seismic phase, according to different sedimentary facies, the corresponding seismic phase changes accordingly. If the seismic phase corresponding to the target interval has the same morphological consistency as the seismic phase corresponding to the formation with the determined sedimentary facies type, and the spreading law is similar, or, if the target formation is sandwiched between the formations corresponding to the two typical signature shape seismic phases, and the seismic phase corresponding to the target interval is similar in morphology to the two typical signature shape seismic phases, then it is determined that the target interval also belongs to the same sedimentary facies type.

[0062] The following Figures 4 - 7 is a further explanation of this step. During the structural interpretation process, the seismic section phase display mode is set to the waveform display form, and by using the mutual conversion of the positive and negative polarities of the seismic phase waveform, typical signature shapes in the positive or negative polarity display mode of the seismic phase are searched near the target interval. As Figure 5 shown, on the A-A1 section, there are two adjacent seismic phases with a wedge shape in the negative polarity setting, as Figure 6 shown, on the B-B1 section, the morphological shapes of these two negative polarity seismic phases are lenticular bodies. As Figure 4 shown, through plane tracing interpretation, these two negative polarity seismic phases intersect and merge into one seismic phase, and the planar projection shape of the intersection point is fan-shaped. This morphological shape of the negative polarity seismic phase (the positive polarity seismic phase does not have this shape) corresponds to the sedimentary environment of the sedimentary facies of the turbidite fan developed in this area. Therefore, it is confirmed that the typical signature shape of this seismic phase corresponds to the morphological shape of the turbidite fan sedimentary geological body, and it is determined that the sedimentary facies of the formation corresponding to the typical signature shape seismic phase is the turbidite fan.

[0063] After it is determined that the sedimentary facies type of the formation corresponding to the typical signature shape seismic phase is the turbidite fan, in the case where the formation corresponding to the typical signature shape seismic phase does not completely coincide with the target interval, by dissecting the cross-section at the center position of the confirmed turbidite fan, as Figure 7 shown, according to different sedimentary facies, the corresponding seismic phase changes accordingly. The seismic phase corresponding to the target interval is adjacent to the upper part of the lenticular body phase and is a seismic phase parallel to the upper phase of the lenticular body, and there is a phenomenon that the seismic phase weakens and thins from the center to both sides. The seismic phase immediately adjacent to the seismic phase corresponding to the target formation also shows an obvious lenticular body shape. Thus, it is determined that the target interval in the target area also belongs to the turbidite fan sedimentary facies type.

[0064] IV. Determine the seismic phase on the seismic section corresponding to the reservoir in the same interval in the target area: Use the logging data and drilling data of the known wells to determine the seismic phase and characteristics corresponding to the sandstone reservoir in the target interval of the target area.

[0065] As a preferred embodiment, in the same structural zone with similar geological conditions near the target area, wells are selected nearby as known wells.

[0066] As a preferred embodiment, using the logging data of the known well, synthetic seismograms are made. Based on the synthetic seismograms and drilling data, the seismic phase corresponding to the target reservoir in the target area on the seismic section is determined.

[0067] As a preferred embodiment, the logging data of the known well is the density curve or the acoustic wave curve.

[0068] As a preferred embodiment, the synthetic seismogram of this well is made through seismic software.

[0069] Then, an optimal embodiment of step four is as follows: First, after determining the sedimentary facies type of the target interval, in the same structural zone with similar geological conditions near the determined target area, wells are selected nearby as the standard wells for the target area. Using the well density curve or acoustic wave curve of this well, the synthetic seismogram of this well is made through seismic software, and a one-to-one correspondence between the strata drilled by this well and the seismic phase of the well-side trace of this well is established. Using the correspondence between the strata drilled by the synthetic seismogram well (standard well) and the seismic phase of the well-side trace of this well, the target sandstone reservoir drilled by the synthetic seismogram well (standard well) and the seismic phase on the corresponding seismic section are determined. Using the relationship between the top and bottom positions of the sandstone reservoir marked on the well trajectory and this seismic phase relationship, the positions corresponding to the top and bottom of the sandstone reservoir on the seismic phase are determined. Then, through the tracing and interpretation of this seismic phase, the seismic phase distribution and characteristics corresponding to the sandstone reservoir in the same interval in the target area on the seismic section are determined.

[0070] The following combines Figures 8 - 11 to further illustrate this step. After determining the sedimentary facies type of the target interval in the target area, near the turbidite fan in the downthrown block of the target fault in the determined target area, well V339 is selected nearby as the standard well for this area. Using the well density curve of well V339, the synthetic seismogram of well V339 is made through seismic software, as Figure 8 shown, and a one-to-one correspondence between the strata drilled by well V339 and the seismic phase of the well-side trace of this well is established, as Figure 9 shown. Using the correspondence between well V339 and the seismic phase of its well-side trace, the target sandstone reservoir drilled by well V339 and the seismic phase on the corresponding seismic section (as Figure 10 shown), and the correspondence between the top and bottom of the sandstone reservoir marked on the well trajectory and this seismic phase are determined. Then, through the tracing and interpretation of this seismic phase, the seismic phase corresponding to the sandstone reservoir in the same interval in the target area on the seismic section of this area and the specific positions corresponding to the top and bottom of the sandstone reservoir on the seismic phase are determined, as Figure 11 shown.

[0071] V. Establishing the target area: Establishing a one-to-one correspondence between the formation lithology density and lithology of the target interval in the target layer: Based on the provenance of the target area and the formation lithology types of the target interval revealed by the wells on both sides, determine the lithology types of the formation in the same interval of the target area, and establish a linear relationship between the formation lithology density and lithology of the target interval in the target area.

[0072] As a preferred implementation method, first, after determining the seismic phase corresponding to the sandstone reservoir in the same interval of the target area and the phase positions corresponding to the top and bottom of the sandstone reservoir, determine the provenance direction of the target area through the sedimentary facies results. Based on the provenance of the target area and the formation lithology types of the target interval revealed by the wells on both sides, determine the lithology types of the formation in the same interval of the target area. Then, use the electric logging density curve data of the surrounding wells to determine the corresponding relationship between the lithology and density of the target interval.

[0073] Specifically, after determining the seismic phase corresponding to the sandstone reservoir in the same interval of the target area and the phase positions corresponding to the top and bottom of the sandstone reservoir, determine the provenance direction of the target area as the western direction through the sedimentary facies results. According to the provenance of the work area and the formation lithology types of the target interval revealed by the wells on both sides, it shows that only sandstone and mudstone are developed in the target interval of the target area. Determine that the lithology types of the formation in the same interval of the target area are sandstone and mudstone. In the target interval where only sandstone and mudstone are developed, the density of mudstone and shale is relatively stable at 2.64 g / cm3, and the density of sandstone varies between 2.4 - 2.6 g / cm3. Therefore, in the case where the lithology types in the target interval are only sandstone and mudstone, the one-to-one correspondence between the formation lithology density and lithology in the target interval of the target area is: high density corresponds to mudstone, and low density corresponds to sandstone.

[0074] VI. Determining the boundary line position of the target reservoir in the target area on the plane map: According to the corresponding relationship between the density and lithology of the formation in the target interval of the target area, under the constraint of sedimentary facies, determine the density distribution corresponding to the sandstone reservoir in the target interval, and combine the seismic phase characteristics corresponding to the sandstone reservoir in the target interval to determine the distribution and boundary line position of the sandstone reservoir in the target interval on the plane map.

[0075] In this embodiment, according to the linear relationship between the formation lithology density and lithology of the target interval in the target area, under the constraint of sedimentary facies, the low-density layer in the target interval is the sandstone reservoir. Therefore, under the setting of the seismic variable density seismic phase display mode, the low-density seismic phase in the target interval is the seismic reflection wave characteristic of the only known low-density sandstone reservoir. Thus, it is determined that the low-density seismic phase in the target interval of the target area corresponds to the sandstone reservoir, solving the problem of multiple solutions for the low-density sandstone reservoir.

[0076] By determining the seismic phase corresponding to the sandstone reservoir in the target interval of the target area in Step 4, this seismic phase shows a low-density seismic phase on the variable-density seismic section. According to the linear relationship between the formation lithology density and lithology in the target interval of the target area, under the constraint of sedimentary facies, it is also determined that the low-density layer in the target interval is the sandstone reservoir. Therefore, the possibility that the target interval is other low-density lithologies is excluded.

[0077] Set the seismic phase display color scale to a multi-color scale method with higher sensitivity (high resolution) to synthesize the seismic variable-density phase color system boundary corresponding to the marked boundary of the sandstone reservoir in the target interval on the well trajectory of the synthetic seismogram as the boundary line of the target sandstone reservoir. Through tracing and interpretation, determine the profile boundary line of the target sandstone reservoir in the target area. Through the continuous tracing and interpretation of this seismic phase, determine the distribution and boundary line position of the target sandstone reservoir in the target area on the plane map.

[0078] The following is combined with Figures 12 - 14 to further illustrate this step. Through Step 5, it is determined that the lithology types in the target interval of the target area are only sandstone and mudstone. Under the constraint of turbidite fan sedimentary facies, it is confirmed that the low-density layer in the target interval is the sandstone reservoir; therefore, under the setting of the seismic variable-density seismic phase display method, as Figure 12 、 13 shown, the variable-density seismic phase with low values of the target interval is the seismic reflection wave characteristic of the low-density sandstone reservoir, thereby determining that the low-density seismic phase in the target interval of the target area corresponds to the sandstone reservoir, solving the problem of multi-solution of the low-density sandstone reservoir.

[0079] By Step 4, it is determined that the seismic phase corresponding to the sandstone reservoir in the target interval of the target area is a low-value variable-density seismic phase, which is displayed by the Min of the color scale of the variable-density seismic section, and the variable-density seismic phase with low values; then through this step, it is determined that the low-value variable-density seismic phase in the target interval corresponds to the sandstone reservoir, excluding the possibility of other low-density lithologies, and setting the seismic phase display color scale to a multi-color scale method with higher sensitivity, as Figure 14 shown, taking the seismic variable-density phase color system boundary corresponding to the marked boundary of the sandstone reservoir in the target interval on the well trajectory of Well V339 as the boundary line of the target sandstone reservoir, and through tracing and interpretation, determining the profile boundary line of the target sandstone reservoir in the target area. Through the continuous tracing and interpretation of this seismic phase, determine the distribution and boundary line position of the target sandstone reservoir in the target area on the plane map.

[0080] VII. Characterize the structural-lithologic composite trap: In Step 2, the structural map of the target interval is determined. In Step 6, the boundary line position of the target sandstone reservoir in the target area on the plane map is determined. Combining the structural map of the target interval with the boundary line position of the sandstone reservoir in the target interval on the plane map, determine the structural-lithologic composite trap.

[0081] As a preferred embodiment, the determined target layer structure map is superposed with the position of the boundary line of the target sandstone reservoir in the target area on the plan view in equal proportion. The trap formed by the combination of faults and the annihilation boundary line of the sandstone reservoir is the characterized structural-lithologic composite trap, as Figure 16 shown.

[0082] In the structural-lithologic composite traps in the favorable areas of the oil and gas enrichment zones, it is conducive to the accumulation and preservation of oil and gas, and is the main target of the rolling exploration of the oilfield. Finding the favorable structural-lithologic composite traps for oil and gas accumulation in the main oil-bearing strata of the oil and gas-rich zones means that the research work on increasing reserves through rolling exploration is completed. Next, the research results are verified by drilling, as Figure 15 shown. The drilling results of the top structural-lithologic composite trap of the target layer verify the effectiveness of the above characterization method.

[0083] When characterizing the structural-lithologic composite oil and gas trap of the present invention, the seismic phase of searching for typical marker morphologies is used to determine the sedimentary facies type of the target area. Under the constraint of the sedimentary facies, according to the provenance of the target area and the lithology types of the target layer segments on both sides, the lithology types of the same layer segments in the target area are determined, and the problem of multi-solution in reservoir prediction is solved. By making synthetic seismograms on wells near the target area, a one-to-one correspondence between the drilled strata of the wells and the seismic phases is established. Through the short-distance seismic phase tracking, the seismic phase corresponding to the target reservoir in the target area is determined, and the risk of increasing errors in the tracking process is reduced. Using the variable density high-sensitivity multi-color scale display method of seismic phases, the boundary of the sandstone reservoir marked by the variable density seismic phase color system corresponding to the well trajectory of the synthetic seismogram well is used to determine the boundary of the target sandstone reservoir, and then the boundary line of the target sandstone reservoir in the target area is determined, making the confirmation of the reservoir lithology boundary quantitative. Then, the sandstone boundary line and the structure map of the same horizon are superposed in equal proportion to complete the characterization of the structural-lithologic composite trap. This characterization method solves the problems of multi-solution, large error, and poor effect existing in the prior art, improves the efficiency, reduces the cost, and has a high accuracy rate for reservoir prediction.

Claims

1. A method for characterizing a structural-lithologic composite trap, characterized in that, the method comprises the following steps: 1) Obtain seismic data of the target area, logging data and drilling data of known wells; 2) Use the seismic data to conduct continuous structural interpretation of the target interval in the target area and produce a structural map of the target interval; 3) During the continuous structural interpretation process, determine the sedimentary facies type of the target area according to the corresponding relationship between the typical iconic shape of the seismic phase and the sedimentary facies type; 4) Use the logging data and drilling data of the known wells to determine the seismic phase and characteristics corresponding to the sandstone reservoir in the target interval of the target area; 5) Based on the provenance of the target area and the drilling data on both sides, determine the lithology types of the strata in the same interval of the target area, and establish a corresponding linear relationship between the lithology density and lithology of the strata in the target interval of the target area; 6) According to the corresponding linear relationship established in step 5), under the constraint of the sedimentary facies in the target area, determine the density distribution corresponding to the sandstone reservoir in the target interval, and combine the seismic phase characteristics corresponding to the sandstone reservoir in the target interval determined in step 4) to determine the distribution and boundary line position of the sandstone reservoir in the target interval on the plane map; 7) Combine the structural map of the target interval with the distribution and boundary line position of the sandstone reservoir in the target interval on the plane map to determine the structural-lithologic composite trap.

2. The method for characterizing a structural-lithologic composite trap according to claim 1, characterized in that, in step 1), the selection method of the target area is as follows: Use the oil and gas distribution map of the oilfield to study the plane law of oil and gas distribution and the oil and gas bearing intervals in the oilfield, and determine the oil and gas enrichment zones and oil and gas bearing intervals in the oilfield; Based on the sedimentary facies results of the oil and gas bearing intervals in the oil and gas enrichment zones, select the target area in the oil and gas accumulation potential areas with the formation conditions of structural-lithologic composite traps.

3. The method for characterizing a structural-lithologic composite trap according to claim 1, characterized in that, in step 3), during the continuous structural seismic interpretation process, under the waveform display mode of the seismic profile phase, use the mutual conversion of the positive and negative polarities of the seismic phase waveform to observe and find the typical iconic shape under the positive or negative polarity display mode of the seismic phase near the target interval, and determine the sedimentary facies type of the target area according to the corresponding relationship between the typical iconic shape of the seismic phase and the sedimentary facies type.

4. The method for characterizing a structural-lithologic composite trap according to claim 3, characterized in that, if the stratum corresponding to the typical iconic shape seismic phase does not completely coincide with the target interval, dissect the cross section at the center position of the typical iconic shape seismic phase. If the seismic phase corresponding to the target interval is consistent with the morphology of the typical iconic shape seismic phase and has a similar distribution law, or if the target stratum is sandwiched between the strata corresponding to the two typical iconic shape seismic phases and the seismic phase corresponding to the target interval is similar to the morphology of the two typical iconic shape seismic phases, then the sedimentary facies type of the stratum corresponding to the typical iconic shape seismic phase is the sedimentary facies type of the target interval in the target area.

5. The method for characterizing a structural-lithologic composite trap according to claim 1, characterized in that, In step 4), the process of determining the seismic phase and characteristics corresponding to the sandstone reservoir in the target interval of the target area using the logging data and drilling data of the known well is as follows: synthetic seismograms are made using the logging data of the known well to establish a one-to-one correspondence between the strata drilled by the known well and the seismic phase of the well-side trace of the well. Using the correspondence between the known well and the seismic phase of the well-side trace of the well, the target sandstone reservoir drilled by the known well and the seismic phase on the corresponding seismic section are determined. Using the relationship between the top and bottom positions of the sandstone reservoir marked on the well trajectory and the seismic phase, the positions corresponding to the top and bottom of the sandstone reservoir on the seismic phase are determined, and the seismic phase is traced and interpreted to determine the distribution and characteristics of the seismic phase corresponding to the sandstone reservoir in the target interval of the target area on the seismic section.

6. The method for depicting a structural-lithologic composite trap according to claim 1, wherein, in step 5), the process of establishing the corresponding linear relationship between the lithology density and lithology in the target interval of the target area is as follows: the provenance direction of the target area is determined through sedimentary facies results. Based on the provenance of the target area and the lithology types of the strata in the target interval revealed by the drilling wells on both sides, the lithology types of the strata in the same interval of the target area are determined. Using the logging density curve data of the surrounding drilling wells, a one-to-one correspondence between the density and lithology in the target interval of the target area is established.

7. The method for depicting a structural-lithologic composite trap according to claim 1, wherein, In the process of determining the position of the boundary line of the sandstone reservoir in the target interval on the plan view, the display color scale of the seismic phase corresponding to the target sandstone reservoir in the target area determined in step 4) is set as a multi-color scale. The seismic variable density phase color system boundary line corresponding to the marked boundary of the sandstone reservoir in the target interval on the well trajectory of the synthetic seismogram well is used as the boundary line of the target sandstone reservoir. Through tracing and interpretation, the boundary line of the target sandstone reservoir profile in the target area is determined; through the continuous tracing and interpretation of the seismic phase, the position of the boundary line of the target sandstone reservoir in the target area on the plan view is determined.

8. The method for depicting a structural-lithologic composite trap according to claim 1, wherein, in step 7), the structural map of the target interval and the position of the boundary line of the sandstone reservoir in the target interval of the target area on the plan view are overlaid in proportion. The trap formed by the combination of faults and the annihilation boundary line of the sandstone reservoir is the depicted structural-lithologic composite trap.

9. The method for depicting a structural-lithologic composite trap according to claim 1, wherein, in step 5), when the lithology types in the target interval of the target area are only sandstone and mudstone, the corresponding relationship between the density and lithology in the target interval of the target area is: high density corresponds to mudstone, and low density corresponds to sandstone.

10. The method for depicting a structural-lithologic composite trap according to any one of claims 1 to 9, wherein, in step 4), the known well is a standard well selected nearby in the same structural zone near the target area.

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